Recently, for laminated piezoelectric elements, in addition to advance of miniaturization, it is requested to obtain stable displacement characteristic even in the case of long-time continuous driving under such severe conditions as high electric field and high pressure. A laminated piezoelectric element has an opposing section where internal electrodes on an anode side and on a cathode side oppose via a piezoelectric layer in the laminating direction, and a non-opposing section which is a portion other than the opposing section. In such a laminated piezoelectric element, since the non-opposing section does not displace while the opposing section displaces during driving, stress tends to be concentrated in this non-opposing section.
For alleviating such stress, for example, there are proposed a laminated piezoelectric element wherein electrode-electrode distance can be varied, a laminated piezoelectric element wherein an overlapping area of internal electrodes near the piezoelectric layer where is piezoelectrically inactive is made smaller than an overlapping area of internal electrodes in other piezoelectrically active part, and a laminated piezoelectric element wherein a site where stress tends to concentrate is provided with a stress alleviating layer filled with lead titanate power.
The conventional laminated piezoelectric elements as described above have stress alleviating effect in non-opposing sections. However, there is a need of a laminated piezoelectric element capable of obtaining more stable displacement characteristic even when it is continuously driven for a long time under severe condition.